Document Detail

Modulation of 17 alpha-hydroxylase/C17,20-lyase activity in porcine theca cells.
MedLine Citation:
PMID:  2788776     Owner:  NLM     Status:  MEDLINE    
The major source of ovarian androgen is the theca cells. Androgens are produced by the conversion of progestins by the 17 alpha-hydroxylase/C17,20 lyase enzymatic system (lyase). The 3 beta-hydroxysteroid dehydrogenase and aromatase enzymes in the theca cells are modulated by gonadotropins as well as by steroids produced locally. Therefore, the combined effects of hCG plus progesterone, estradiol, or dihydrotestosterone (DHT) on microsomal lyase activity in theca cells from large and medium-sized follicles were determined. Theca cells (3 x 10(6) cells/6 ml/well) were cultured in Medium 199 (M199) containing only insulin (10 micrograms/ml) and transferrin (5 micrograms/ml). At 24 h, theca cells were treated with M199, hCG (15 ng/ml), progesterone, estradiol, or DHT (100 ng/ml) or a combination of hCG + one of the three steroids. Media were removed at various times of culture (27-72 h) and levels of androgen determined by RIA. Microsomes were incubated with 1 microCi [3H]progesterone +0.5 mM NADPH and radioactive conversion products were measured after purification by thin layer chromatography. Administration of progesterone, estradiol, or DHT alone had little effect on lyase activity in theca cells from medium-sized follicles whereas the addition of hCG alone significantly increased lyase activity in these cells. However, concomitant addition of any steroid with hCG inhibited the increase in lyase activity after the addition of hCG alone. Theca cells from large porcine follicles had a higher basal level of lyase activity compared to theca cells from the smaller follicles. Lyase activity in theca cells from large follicles was enhanced by progesterone; estradiol was inhibitory. DHT initially stimulated lyase activity in theca cells from large follicles, but was inhibitory later in culture. In contrast to its marked effect on theca cells from medium follicles, hCG had only a small effect on lyase activity in theca cells from large follicles. Thus, thecal lyase activity increased as the follicle matured, providing more androgen substrate for the production of estrogen. Lyase activity in theca cells of medium follicles appears to be regulated predominantly by gonadotropin from the pituitary while intraovarian regulation of lyase activity by steroids may be more important in larger follicles.
S A Tonetta; M Hernandez
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of steroid biochemistry     Volume:  33     ISSN:  0022-4731     ISO Abbreviation:  J. Steroid Biochem.     Publication Date:  1989 Aug 
Date Detail:
Created Date:  1989-09-29     Completed Date:  1989-09-29     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0260125     Medline TA:  J Steroid Biochem     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  263-70     Citation Subset:  IM    
Livingston Research Laboratory, Department of Obstetrics and Gynecology, University of Southern California School of Medicine, Los Angeles 90033.
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MeSH Terms
Aldehyde-Lyases / metabolism*
Cells, Cultured
Chorionic Gonadotropin / physiology
Cytochrome P-450 Enzyme System / metabolism*
Microsomes / enzymology
Steroid 17-alpha-Hydroxylase / metabolism*
Steroid Hydroxylases / metabolism*
Steroids / metabolism*
Theca Cells / enzymology*
Reg. No./Substance:
0/Chorionic Gonadotropin; 0/Steroids; 9035-51-2/Cytochrome P-450 Enzyme System; EC 1.14.-/Steroid Hydroxylases; EC 17-alpha-Hydroxylase; EC 4.1.2.-/Aldehyde-Lyases

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